Double threaded standoff fastener

ABSTRACT

Presently disclosed is a standoff fastener for use in a compound floor structure. The threaded fastener includes a threaded standoff portion designed to accept a nut which has a diameter larger than a head portion of the standoff fastener. The head portion is located centrally within the fastener in order to reduce a tendency of the fastener to pivot within a driver during the fastening process.

This application is a continuation of U.S. patent application Ser. No.15/584,383 filed on May 2, 2017, which claims priority to, and thebenefit of, U.S. Provisional Application No. 62/330,633 filed on May 2,2016 with the United States Patent Office, which are both herebyincorporated by reference.

BACKGROUND AND SUMMARY

The present disclosure relates generally to threaded fasteners forcompound floor structures. Cement corrugated floor may be constructed byplacing corrugated sheet steel over a framework of trusses and otherload bearing structures. The corrugated sheet may be electrified andreinforcing rods positioned for welding to the corrugated sheet, forminga compound floor structure. Cement is then poured and hardens aroundstandoff fasteners and/or other reinforcing rods. As the cement hardens,the standoff fasteners act to grip the cement and increase the strengthof the compound floor structure.

Threaded standoff fasteners have been configured with an end headportion designed to accept torque from a driver. An example of such astandoff fastener is described in U.S. Pat. No. 5,605,423. A problemwith such standoff fasteners has been that the head portion is locatedon the end of the fastener creating unwanted torque that moves thefastener away from a desired location. During installation a driverencapsulates the head, leaving a majority of the fastener's structureotherwise exposed. As a result, the fastener structure acts as a leverarm against the driver and has a tendency to rotate out of contact withthe driver during engagement with a subfloor. There is a need for animproved fastener which enables a more efficient method of installingstandoffs without unwanted rotation out of alignment.

Another problem with previous standoff fasteners is that the diameter ofthe fastener was relatively limited. As the diameter of the fastenerincreases, the general strength of the finished composite floorstructure may be increased. This is especially true for the end portionextending above the corrugated material, and the portion in directcontact with the corrugated material. However, configurations ofstandoff fasteners limit the diameter of the standoff portion to lessthan the major diameter of the head portion designed to transfer torque.Further, a single integral standoff fastener with a large diameter isexpensive to produce and not economically feasible given the number offasteners required for a composite floor. Accordingly, there is a needto increase the diameter of the standoff fastener in a cost-effectiveand efficient manner.

Presently disclosed is a standoff fastener having a head portion locatedbetween a screw portion and a standoff portion having threads. An anchorportion or anchor nut may be threaded onto the standoff portion afterthe fastener is fixed in the corrugated subfloor. In this manner, theanchor nut may have a diameter larger than the head portion of thefastener. The placement of the head portion between the screw portionand standoff portion decrease movement of the fastener within a socketdriver and increases end use control of the fastener. This improvesinstallation speed and reduces cost.

Presently disclosed is a fastener comprising a head portion disposedbetween a screw portion and a standoff portion; the head portion havinga key shape which is selected from a group consisting of lobular,splinular, and polygonal; the key shape capable of accepting torque froma driver oriented on drive axis of the fastener; the standoff portionbeing longer than the screw portion, the standoff portion having athreaded segment, where a diameter of the standoff portion is less thanor equal to a diameter of the head portion; the screw portion includinga fluted lead end, and a thread-forming portion having lobes adapted toenable formation of threads into a metal structure.

Also disclosed is a fastener, where the key shape is lobular and has atleast 5 lobes.

Further disclosed is a fastener, where the key shape is splinular andhas at least 5 splines.

Additionally disclosed is a fastener where the key shape is polygonaland has at least 5 sides.

Further disclosed is a fastener, where the screw portion has a firstthread and the standoff portion includes a second thread which isdifferent from the first thread.

Also disclosed is a fastener, where the screw portion has a first threadand the standoff portion includes a second thread which is the same asthe first thread.

Additionally disclosed is a fastener, where an anchor nut with adiameter larger than the diameter of the head portion is attached to thethreads of the standoff portion.

Further disclosed is a fastener, where the head portion furthercomprises a seat portion having a diameter larger than the diameter ofthe head portion, the seat portion located on a side of the head portionclosest to the screw portion.

Additionally disclosed is a fastener, where a second standoff portion isplaced between the head portion and the screw portion.

Further disclosed is a fastener, where the threads of the standoffportion extend up to 90% of a length of the standoff portion.

Also disclosed is an embodiment of a fastener comprising: a headportion, a screw portion including a fluted lead end, an anchor portion,and a shank portion; the fastener having a total length, defined by atip of the fluted lead end and an end of the anchor portion; the headportion disposed away from the tip of the fluted lead end no more than50% of the total length, the head portion having a key shape which isselected from a group consisting of lobular, splinular, and polygonal;the key shape capable of accepting torque from a driver oriented ondrive axis of the fastener; the standoff portion being longer than thescrew portion, the standoff portion having a threaded segment, where adiameter of the standoff portion is less than or equal to a diameter ofthe head portion;

Also disclosed is a fastener, where the screw portion includes athread-forming portion having lobes adapted to enable formation ofthreads into a metal structure.

Additionally disclosed is a fastener, where the key shape is lobular andhas at least 4 lobes.

Further disclosed is a fastener, where the key shape is splinular andhas at least 4 splines.

Additionally disclosed is a fastener, where the key shape is polygonaland has at least 4 sides.

Also disclosed is a fastener, where the screw portion has a first threadand the standoff portion includes a second thread which is differentfrom the first thread.

Further disclosed is a fastener, where the screw portion has a firstthread and the standoff portion includes a second thread which is thesame as the first thread.

Additionally disclosed is a fastener, where an anchor nut with adiameter larger than the diameter of the head portion is attached to thethreads of the standoff portion.

Further disclosed is a fastener, where the head portion furthercomprises a seat portion having a diameter larger than the diameter ofthe head portion, the seat portion located on a side of the head portionclosest to the screw portion.

Also disclosed is a fastener, where a second standoff portion is placedbetween the head portion and the screw portion.

Further disclosed is a fastener, where the threads of the standoffportion extend up to 90% of a length of the standoff portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the accompanying drawings in which particularembodiments and further benefits of the invention are illustrated asdescribed in more detail in the description below, in which:

FIG. 1 is a side view of a fastener with a threaded standoff portion;

FIG. 2 is a side view of a fastener with a partially threaded standoffportion;

FIG. 3 is a side view of a fastener with a head portion in the center oftwo shank portions;

FIG. 4 is a side view of a standoff fastener engaged by a fastener;

FIG. 5 is a side view of a dome shaped fastener;

FIG. 6 is a side view of a ribbed standoff portion;

FIG. 7A is a side view of a multi-head standoff fastener;

FIG. 7B is a cutaway view of an embodiment encased in a buildingmaterial;

FIG. 7C is a side view of a multi-head standoff fastener;

FIG. 8 is a side view of an anchor nut attached to a double threadedfastener;

FIG. 9 is a cutaway view of an embodiment encased in a buildingmaterial;

FIGS. 10A and 10B are side and top views of a disc anchor;

FIGS. 11A and 11B are side and top views of a capped anchor;

FIGS. 12A and 12B are side and top views of an anchor;

FIGS. 13A-13G are top views of various key shapes;

FIGS. 14A-14C are top views of key shapes and their major and minordiameters;

FIG. 15 is a partial prospective view of a floor joist system of thepresent disclosure;

FIG. 16 is a partial prospective view of an alternative embodiment ofthe floor joist system of FIG. 15 ;

FIGS. 17A-17C are side and end views of a thread-forming fastener of thepresent disclosure;

FIGS. 17D-17E illustrate alternative thread-forming portions of thefastener of FIG. 17A;

FIGS. 17F-17G illustrate alternative cross-sections through thethread-forming portion shown in FIGS. 17D and 17E;

FIGS. 18A-18C illustrate side and end views of a thread-forming fastenerof the present disclosure;

FIGS. 19A-19D illustrate side and end views of an alternativeself-drilling, thread-forming fastener of the present disclosure;

FIGS. 20A and 20B illustrate a side view and front view of a standofffastener;

FIG. 21 Illustrates a side view of a standoff fastener;

FIG. 22 illustrates a side view of a standoff fastener with a centrallylocated head portion;

FIG. 23 is a graph of torque over time during installation representingthe thread-forming fastener of FIG. 17A installed in a steel sheethaving a thickness of about 0.25 inch;

FIG. 24 is a graph of torque over time during installation representingalternative thread-forming fasteners of FIG. 17A installed in a steelsheet having a thickness of about 0.25 inch;

FIG. 25 is a graph of torque over time during installation for acomparative self-drilling fastener installed in a steel sheet having athickness of about 0.25 inch;

FIG. 26A is a graph of thread-forming torque, failure torque, andfailure to thread-forming torque ratios for a ¼ inch major diameter selfdrilling, thread-forming fastener of FIG. 18A and a comparative sampleinstalled in steel sheets of various thicknesses;

FIG. 26B is a graph of thread-forming torque, failure torque, andfailure to thread-forming torque ratios for a ⅜ inch major diameter selfdrilling, thread-forming fastener of FIG. 18A and a comparative sampleinstalled in steel sheets of various thicknesses;

FIG. 27 is a graph of torque to over time during installation for theself-drilling, thread-forming fastener of FIG. 18A installed in twosteel sheets having a combined thickness of about 0.06 inch;

FIG. 28 is a graph of torque to over time during installation foralternative self-drilling, thread-forming fasteners of FIG. 18Ainstalled in two steel sheets having a combined thickness of about 0.06inch;

FIG. 29 is a graph of torque to over time during installation for acomparative self-drilling fastener installed in two steel sheets havinga combined thickness of about 0.06 inch;

FIGS. 30A through 30D are graphs of seating torque calculated for ¼ inchself-drilling, thread-forming fasteners and comparative samples forvarious material thicknesses;

FIG. 31 is a graph of torque to over time during installation for theself-drilling, thread-forming fastener of FIG. 18A installed in a steelsheet having a thickness of about 0.187 inch;

FIG. 32 is a graph of torque to over time during installation for acomparative self-drilling fastener installed in a steel sheet having athickness of about 0.187 inch;

FIGS. 33A and 33B illustrate a flush mounted joist seat; and

FIGS. 34A and 34B illustrate an alternative joist seat.

DETAILED DESCRIPTION OF THE DRAWINGS

Generally, a standoff fastener acts to prevent lateral movement of ahardened concrete slab in a finished compound floor structure. Thestandoff fastener is attached perpendicular to a corrugated metalsubfloor, and concrete material is poured over the metal subfloorencapsulating the standoff fastener. The part of the standoff fastenerencapsulated by the concrete is the anchor portion, which increases thegeneral strength of the compound floor structure. This is accomplishedby the anchor portion having a larger diameter than other portions ofthe standoff fastener. As the concrete material forms around thefastener, the anchor portion by virtue of the larger diameter will makethe entire floor structure resist lateral movement.

As shown in FIG. 1 , a doubled threaded standoff fastener 100 is alignedgenerally along a central axis 114. A standoff portion 116 has an endportion 112, and a shank portion 102 which is attached to the headportion 104. The head portion 104 may have a key shape and a seat 106.The key shape is sufficient to enable torque to be transmitted to thestandoff fastener 100 through the head portion with a driver. The seat106 of the standoff fastener 100 transmits lateral force from the driverto the standoff fastener 100. A large deep socket driver presses againstthe seat 106 parallel to the central axis 114 (in addition to rotationalforces) and force the standoff fastener 100 into the corrugated metalsubfloor.

A screw portion 108 with a lead end portion 110 is attached to the seatportion 106. The lead end portion 110 is designed to drill a hole into acorrugated metal subfloor, or may thread into a pre-existing hole. Thescrew portion 108 may have a variety of different kinds of threads, suchas thread forming or thread cutting. Thread forming is understood toinvolve the displacement of material as a standoff fastener threads intoa structure. Thread cutting is known remove material from the underlyingmetal sheet in order to thread into a structure.

A thread may extend the majority of a length of the standoff portion116. The thread of the standoff portion 116 may be the same thread or adifferent thread as in the screw portion 108. The standoff portion 116is not driven through underlying metal subfloor structure. Rather, thethreading in the standoff portion 116 may accept an anchor nut toincrease the surface area exposed to poured concrete.

As shown in FIG. 2 , a double threaded standoff fastener 120 has astandoff portion 138 with end portion 122, a threaded portion 124, aring portion 126, and a shank portion 128. The threaded portion 124 maybe designed to accept an anchor nut which has similar threads. The ringportion 126 prevents the anchor nut from rotating into the shank 128,and may engage and lock the anchor nut.

The head portion 130 may contain a seat 132, which is located adjacentto the screw portion 134 and lead end portion 136. The head portion mayhave a major and a minor diameter, measured perpendicular to the centralaxis 123 of the standoff fastener 120. The major diameter is the largestmeasurable diameter in the head portion, while the minor diameter is thesmallest measurable diameter in the head portion. In some embodiments,the lead end 136 may be fluted. The major and minor diameter may also beas described in FIGS. 14A, 14B, and the accompanying text.

It is contemplated that the thread type of the threaded portion 124 maybe of a different type of threading than the screw portion 134. Forexample, the threads of the threaded portion 124 could have a higher orlower thread count. In this embodiment, the threaded portion 124 wouldhave a first thread type, and the screw portion 134 would have a secondthread type. In some other embodiments, the threads may be of the sametype.

Further, the threaded portion 124 may comprise only a portion of thelength of the standoff portion 138. In some embodiments, the threadedportion 124 may extend from the end portion 122 down to 90% of thelength of the standoff portion. Alternatively, the threaded portion mayextend 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the length ofthe standoff portion.

As shown in FIG. 3 , a double threaded standoff fastener 140 may have astandoff portion 143 with a first shank portion 146 and a second shankportion 150. A head portion 148 having a key shape may be disposedbetween the first shank portion 146 and second shank portion 150. Thestandoff portion 143 may also have an end portion 142 and a runout 158placed between a threaded portion 144 and first shank portion 146. Inone embodiment, the seat 152 is separate from the head 148 and locatedbetween the second shank portion 150 and screw portion 154, which a leadend portion 156 attached to the screw portion 154.

The threaded portion 144 may have a first kind of thread, and the screwportion 154 may have a second kind of thread. In some embodiments, thethread located on the threaded portion 144 and screw portion 154 is thesame. In other embodiments, they are different.

As shown in FIG. 4 , a threaded standoff fastener 160 is driven into asubstrate 176 by a driver 163. The substrate 176 is preferablycorrugated steel subfloor and the driver 163 is preferably a deepsocket. The components of the standoff fastener 160 may be aligned on adrive axis 178.

The threaded standoff fastener 160 includes a standoff portion 165 whichis located above the substrate 176 after the fastener 160 has beenfastened. The standoff portion 165 may have a seat potion 170, and ananchor portion 162 having a diameter larger than a first shank portion164 and second shank portion 168. A head portion 166 having a key shapeand a major diameter greater than the anchor portion 162 is disposedbetween the first shank portion 164 and second shank portion 168. Belowthe standoff portion 165 is a threaded portion 172 and lead end 174.

The standoff fastener 160 has a total length “J” with the anchor portion162 defining one end and the tip of the lead end 174 defining the otherend. The seat portion 170 is disposed a distance “I” along the driveaxis 178 measured from the tip of the fluted lead end 174. The headportion 166 is located a distance “H” away from the seat portion 170along the drive axis 178.

Because the driver 163 applies a lateral force F on the seat 170, thedistance I represents the lever arm of the fastener. Minimizing “I” willincrease the amount of force F that can be applied to the fastener 160without the fastener coming loose or slipping along the substrate 176.

The driver 163 applies a rotational torque through the head portion 166while applying the lateral force F on the seat 170. The distance betweenwhere the rotational torque is applied relative to the lateral force Falong the drive axis 178 is the distance H. As the value of H increases,the ability of the fastener to pivot within the driver 163 is decreased.Increasing the value of H will make the fastener easier to control.

FIG. 5 illustrates a standoff fastener 230 with a standoff portion 244,dome portion 232, shank portion 234, head portion 236, seat portion 238,screw portion 240, and lead end portion 242. The components of thestandoff fastener 230 may be generally aligned on a drive axis 246.

The dome portion 232 has a diameter “B,” the shank portion 234 has adiameter “C,” the head portion 236 has a minor diameter “D,” and theseat portion 238 has a diameter “F.” The diameters may be measured in adirection perpendicular to the drive axis 246. In some embodiments, asocket driver fits over the dome portion 232 and shank portion 234 toengage with the key shape of the head portion 236. Since the socketdriver is usually a straight tube, the diameter B must be of lesser orequal value to the diameter D. In a preferred embodiment, the diameter Cis less than B, D, and F. The seat portion 238 is larger than the headportion 236 so it may accept a later force (or a force substantiallyparallel to the drive axis 246) from the socket driver. Accordingly, thediameter F may be larger than the diameter D.

The standoff fastener 230 has a total length L, measured along the driveaxis 246 from the tip of the lead end 242 to the end of the dome portion232. The dome portion 232 has a depth A, the head portion 236 and seatportion 238 have a combined depth E, and the threaded portion 240 andlead end portion 242 have a combined depth G.

FIG. 6 illustrates a ribbed standoff fastener 250 with a standoffportion 266, dome end portion 252, shank portion 254, ribbed portion256, head portion 258, seat portion 260, screw portion 262, and a leadend portion 264.

The ribbed portion 256 contains a plurality of ribs or raised ridgeswhich are parallel to one another. They function to increase the surfacearea of the standoff structure located between the dome end portion 252and the head portion 258. The increased surface area effectively grips apoured and hardened concretious material and will make the standofffastener resist motion while inside the hardened concrete. The ribbingis not threaded, meaning that a nut or other member cannot berotationally fastened onto the ribbed portion 256.

FIGS. 7A and 7C illustrate a doubled threaded standoff fastener 270,having a standoff portion 271, end portion 272, first thread end 274, afirst shank portion 276, first head portion 278, second shank portion280, second head portion 282, a seat 284, a second thread end 286, and alead end 288.

As further illustrated by FIG. 7C, the standoff fastener 270 can accepta driver of at least two different sizes by virtue of the separate headportions. The first head portion 278 has a smaller major diameter thanthe second head portion 282. While both head portions are illustratedwith a hex key shape in FIG. 7A, it is contemplated that the headportions could include a variety of key shapes, as illustrated by FIG.7C. Since the first head portion 278 has a larger diameter than thesecond shank portion 280, as illustrated in both FIGS. 7A and 7C, thefirst head portion 278 may also act as anchor portion enabling thefastener 304, that is fastened into a steel subfloor 308 of a floorassembly 300, to resist lateral movement when encased in a hardenedconcrete 302, as further illustrated by FIG. 7B.

FIG. 8 illustrates an assembly 290 of an anchor nut 292 threaded onto adouble threaded fastener 294. In this assembled configuration, a socketdriver would be unable to engage with the head portion of the fastener294 by virtue of the larger diameter of the anchor nut. By placing theanchor nut onto the fastener after it has been fastened into acorrugated metal subfloor, the anchor portion of a fastener can have adiameter much larger and unbounded by the diameter of the head portion.This embodiment still retains the advantages of locating the headportion within the interior of the fastener as whole, such as increasedlateral force and control.

FIG. 9 illustrates a floor assembly 300, having a plurality of standofffasteners 304 fastened into steel subfloor 308, each fastener having ananchor nut 306. The standoff fasteners and anchor nuts are encapsulatedby a cementious material.

FIGS. 10A and 10B illustrate an anchor nut 200 with a cap 202, a headportion 204 having a key shape, and disc portion 206. The disc portion206 has a diameter which is substantially greater than the diameter ofthe head portion 204.

FIGS. 11A and 11B illustrate an anchor nut 210 with a cap 212, headportion 214, and seat portion 216. The seat portion 216 has a diameterwhich is greater than or equal to a diameter of the head portion 214,and is in some embodiments circular in shape. It is contemplated than ananchor nut could take many forms, as long as the nut has a diametergreater than the shank portion and threading designed to attach to thestandoff fastener.

FIGS. 12A and 12B illustrates an anchor nut 220 with a head portion 222having a key shape and a seat portion 224, which a central hole 226 witha thread form inside.

As shown generally in FIGS. 13A-13G, a head portion of the instantfastener may be of a variety of key shapes, such as hexalobular 182(i.e. five lobes), hexagonal 184 (i.e. six sides), pentalobular 186(i.e. five lobes), pentagonal 188 (i.e., five sides), quadralobular 190(i.e., four lobes), quadraspinular 192 (i.e., four splines), orhexaspinular 194 (i.e. five splines). It is contemplated that at leastthese general key shapes are appropriate for both the standoff fastenersand the anchor nuts of the present disclosure. While the disclosureillustrates fasteners using the hexagonal key shape, a person ofordinary skill in the art understands that the key shape can be anyshape desired.

By way of illustration, a selection of fastener recesses are illustratedin FIGS. 14A-14C. The fastener socket recess shown in FIG. 14A is ahexalobular socket 320 appropriate for use with the hexalobular key 182of FIG. 13A. Alternatively, the fastener socket recess shown in FIG. 14Bis a hexagonal shape 330 appropriate for use with the hexagonal key 184or Allen key of FIG. 13B. The fastener socket recess shown in FIG. 14Cis a pentalobular socket 331 appropriate for use with the pentalobularkey 186 shown in FIG. 13C. As will be apparent, each key shape fits oneor more socket recesses in desired fasteners.

In any case, the fastener socket recess has a major dimension M and aminor dimension N as shown in FIG. 14A. The major dimension M is thedimension of the socket extending between opposing lobes 326, 322 on thehexalobular socket illustrated. The minor dimension N is the dimensionof the socket extending between opposing spaces or antilobes 328, 324between the lobes.

More generally, the major dimension of a fastener may be defined as thediameter of a circle centered on the longitudinal axis of the fastenerand having a radius extending from the longitudinal axis to a point onthe perimeter of the socket recess furthest from the longitudinal axisof the fastener. The minor dimension may be defined as the diameter of acircle centered on the longitudinal axis of the fastener and having aradius extending from the longitudinal axis to a point on the perimeterof the socket closest to the longitudinal axis of the fastener. By wayof illustration, the hexagonal socket recess 330 has a major dimension Mand a minor dimension N as shown in FIG. 14B. A pentalobular socket 331has a major dimension M and a minor dimension N as shown in FIG. 14C. Itis contemplated that the manner in which M and N are measured wouldapply to any key shape, regardless if the key shape is represented in anegatively oriented recess or positively oriented drive head.

Turning now to FIGS. 15 and 16 , a building structure may include afloor joist system 400 and at least one load and typically two or morebearing member 410. The floor joist system 400 may comprise a pluralityof joists 394 transverse to the load bearing member 410 spaced betweenload bearing members 410, and supporting a steel deck 382. The steeldeck 382 is typically made of side-by-side corrugated member, covered bya concrete slab 384. The load bearing member 410 may include a girder386 as shown in FIG. 15 . Alternatively, the load bearing member 410 maybe a load bearing wall 380 comprising a plurality of studs 382 as shownin FIG. 16 . The load bearing member may comprise other structuralmembers as desired to support the floor joist system 400.

Various building members in the building structure may be connectedtogether and secured by a plurality of thread-forming fasteners 388 suchas shown in FIG. 17A, or by a plurality of self-drilling, thread-formingfastener 362 such as shown in FIG. 18A, or by a plurality of casehardened thread-forming self-drilling fasteners such as shown in FIG.19A. For example, a first steel building member, such as a joist 394,may be connected to a second steel building member, such as the loadbearing member 410, by a plurality of the thread-forming fasteners 388,or by a plurality of the self-drilling, thread-forming fastener 362.

Each thread-forming fastener 388 is a fastener of steel having a taperedlead portion 346 tapering at an angle in a range from 30° to 60° of atleast Rockwell C-Scale hardness (HRC) 50 induction hardness adapted tostart into a pilot hole 378, which may be pre-drilled, pre-punched orotherwise formed, in at least the second steel building member, such asshown in FIGS. 31A, 31B, 32A, and 32B. The thread-forming fastener 388includes a thread-forming portion 350 of at least HRC 50 hardnessadapted to thread the fastener 388 into at least the second buildingmember, and a threaded portion 348 adjacent the thread-forming portion350. As used in the specification herein and the appended claims, theword adjacent means either adjoining or nearby; as used herein adjacentfeatures may or may not be contiguous. The thread-forming fastener 388has a head 354 capable of clamping the first steel building member tothe second steel building member with the fastener 388 installed. Thethreaded portion 348 has a major diameter 342, i.e. the diameter of thefastener at the tip of the thread, and a minor diameter 340, i.e. thediameter of the fastener at the root of the thread, as shown in FIG.17C. The fastener 388 has a desired thread pitch 344, i.e. the distancefrom one thread tip to the adjacent thread tip along the length of thefastener, as shown in FIG. 15C.

At least a portion of the threaded portion 348 of the thread-formingfasteners 388 adjacent the head 354 may have a hardness between aboutRockwell B-Scale hardness (HRB) 70 and HRC 40. In one alternative, atleast a portion of the threaded portion 348 has a through hardnessbetween about HRC 25 and HRC 34. In one alternative, at least a portionof the threaded portion 348 has a through hardness between about HRB 70and HRB 100. In one alternative, at least a portion of the threadedportion 348 has a through hardness between about HRC 19 and HRC 30. Inone alternative, at least a portion of the threaded portion 348 has athrough hardness between about HRC 26 and HRC 36. In yet anotheralternative, at least a portion of the threaded portion 348 has athrough hardness between about HRC 33 and HRC 39. The hardness of atleast a portion of the threaded portion 348 may be selected to complywith ASTM A307, ASTM A325, ASTM A354, ASTM A490 or other fastenerstandard. Alternatively or in addition, the hardness of at least aportion of the threaded portion 348 may be selected to comply with SAEJ429 Grade 2, SAE J429 Grade 5, and SAE J429 Grade 8, or other fastenerstandard. Adjacent the threaded portion 348, the thread-forming portion350 may have a hardness greater than about HRC 50, and may be greaterthan about HRC 54. Up to five threads between the threaded portion 348and the thread-forming portion 350 may be hardened to at least HRC 50 orat least HRC 54, and at least a majority of the threaded portion 348 ofthe thread-forming fasteners 388 is through-hardened such that thefastener is ductile through the threaded portion. As the thread-formingfastener 388 is installed connecting a first steel building member and asecond steel building member, the fastener 388 may be tightened to clampthe first member between the head 354 and the formed threads in thesecond building member. As the thread-forming fastener 388 is tightened,a portion of the ductile threaded portion 348 between the head 354 andthe threads engaging the second building member elongates providing aclamping load on the connection according to design requirements. In thepast, thread-forming fasteners had case hardened threads that could notelongate in clamping without risk of fracture or hydrogen embrittlement.The present thread-forming fasteners 388 have sufficient ductility forstructural connections such as slip-critical connections in which thematerials joined are clamped together without slippage by the tensioninduced in the fasteners.

The thread-forming fastener 388 may have a major diameter between about¼ inch, or smaller, and 1½ inch, or larger. In a connection of first andsecond steel building members, the first steel building member may havea clearance hole 380 having a diameter larger than the major diameter ofthe fastener 388. The second steel building member has the pilot hole378 aligned with the clearance hole in the first member, the pilot holebeing smaller than the major diameter of the fastener 388, and typicallylarger than the minor diameter, although for thin metal applications,such as thinner than 14 gage, or less than 16 gage, the pilot hole maybe smaller than the minor diameter. The pre-drilled or pre-punched pilotholes 378 in the second steel building member may be adapted toinstalling thread-forming fasteners 388, the pilot holes 378 having abore diameter between about 70% and 98% of the major diameter 342.Alternatively, the pilot hole bore diameters for installing thethread-forming fasteners 388 may be between about 80% and 98% of themajor diameter 342, and alternatively between about 80% and 95% of themajor diameter. The diameter of the pilot hole may be selected based onthe thickness of the second building member, the major diameter of thefastener, and the desired thread-forming torque. The thread-formingfastener 388 is installed through the clearance hole 380 and rotatedinto the pilot hole 378. The thread-forming portion 350 forms threads inthe bore of the pilot hole for the threaded portion 348 to engage thesecond member. The thread-forming fastener 388 is tightened to clamp thefirst member between the head 354 and the formed threads in the secondmember. Alternatively, the first and second members are both providedwith pilot holes and the thread-forming portion 350 forms threads in thebore of the pilot holes in both the first and second members for thethreaded portion 348 to engage the first and the second member.Optionally, the thread-forming fastener 388 may include an unthreadedshank portion between the head 354 and the threaded portion 348 asdesired for the connection. If provided, the length of an unthreadedshank portion and the axial length of the threaded portion 348 may beselected according to the thickness of the first and second buildingmembers and desired length of thread engagement. For example, in certainbearing-type connections with threads excluded from the shear plane, anunthreaded shank portion may be desired having a length greater than thethickness of the first building member such that the threaded portion348 engages the second building member clamping the first buildingmember between the head 354 and the threads engaging the second buildingmember. In any case, the threaded engagement with the first and/orsecond building member acts as a nut, and in certain applications, nonut may be required based on design requirements. Examples of variousconfigurations of installation of thread-forming fasteners 388 clearanceholes and pilot holes are disclosed in applications described herein,and each application disclosed is not limited to the configurationdescribed.

Shown in the graph of FIG. 23 is the installation torque over time for 5test samples of the self-drilling, thread-forming fastener 362identified as manufacturer's samples 360-80901-60, representative of thethread-forming portion and threaded portion of the thread-formingfastener 388 having a major diameter of ⅜ inch installed into a pilothole at 175 revolutions per minute into a ¼ inch thick plate. As thethread-forming fastener 388 is driven into the pilot hole in the ¼ inchthick plate, a thread-forming torque 426 is the largest torque used torotate the thread-forming portion 350 of the thread-forming fastener 388into the pilot hole 378 forming threads in the pilot hole. After thehead 354 makes contact with the first building member, further rotationadvances the threaded portion 348 into the threaded fastener openingwith increasing torque as the head clamps the members against thethreads formed in the second member. The operator stops tightening thefastener at a seating torque 422 as desired lower than the failuretorque 420. The drive torque 424 is the torque right before the torquerise to seating, as shown in FIG. 23 . Continued rotation of thefastener may further increase the torque needed to turn the fasteneruntil the bolted connection fails at the failure torque 420. The failuremode typically is determined by the thickness of the building membersand the major diameter 342 of the fastener. When the building member inwhich threads are formed is a thin material such as less than 14 gage,or less than 16 gage, the material of the building member may deform orfracture and the fastener strip-out at a strip torque. Failure torque420 generally refers to strip torque in building members of thinnerthickness. For certain material thicknesses, the fastener will fractureat the failure torque 420.

The installation torque over time for the thread-forming fastener 388was measured using self-drilling, thread-forming fasteners 362 installedin a pre-drilled pilot hole to negate effects of the fluted leadportion. Five samples having a major diameter of ⅜ inch were installedat 175 revolutions per minute into pilot holes in a steel member havinga thickness of about 0.25 inch and plotted in the graph of FIG. 23 . Thethread-forming torque 426 as shown in the graph of FIG. 23 is less thanabout 200 inch-pounds. The drive torque 424, before the torque rises toseating, is less than about 25 inch-pounds. The failure torque 420 isgreater than 343.94 inch-pounds. For certain samples, the failure torqueis greater than 700 inch-pounds, and one sample greater than about 900inch-pounds. The failure torque 420 shown in FIG. 23 is a strip torquefor 4 of the 5 samples. The trace identified as “A” in FIG. 23 shows adrop to 0 inch-pounds after reaching the failure torque because fastenerA fractured at the failure torque. The ratio of failure torque tothread-forming torque is at least 3.0, and the ratio of failure torqueto drive torque may be greater than 6.0 when the steel member has athickness of 0.25 inch (about 6.35 millimeter) and the pilot hole havingat least one diameter within nominal diameter between 85 and 90% ofmajor diameter. Alternatively, the ratio of failure torque to drivetorque may be greater than 10, and may be greater than 20. The ratio offailure torque to drive torque may be as high as 50 to 100, or more,when the second building member having a thickness of 0.25 inch and thepilot hole having at least one diameter within nominal diameter between80 and 98% of major diameter.

Further testing of ⅜ inch major diameter thread-forming fasteners 388 isshown in FIG. 24 . As with the experiment shown in FIG. 23 , theinstallation torque over time for the thread-forming fastener 388 wasmeasured using ten samples of self-drilling, thread-forming fasteners362, identified as manufacturer's samples 360-80952-60 having a majordiameter of ⅜ inch, installed in pre-drilled pilot holes to negateeffects of the fluted lead portion. The samples were installed at 175revolutions per minute into 0.302 inch diameter pilot holes in a steelmember having a thickness of about 0.25 inch and plotted in the graph ofFIG. 24 . In this test sample, the average thread-forming torque 426 ofthe samples was 316.6 inch-pounds. As shown in the graph of FIG. 24 ,the thread-forming torque is less than about 350 inch-pounds. The drivetorque 424, before the torque rises to seating, is less than about 100inch-pounds. The failure torque 420 is greater than 600 inch-pounds. Forcertain samples, the failure torque is greater than 700 inch-pounds, andone sample greater than 800 inch-pounds.

FIG. 25 shows installation torque over time for comparative samples ofprior ⅜ inch fasteners. The comparative fasteners lacked the presentthread-forming portion, instead utilizing prior technology. The graph ofFIG. 25 shows the higher thread-forming torque required to drive theprior fasteners. The average thread-forming torque of the ten sampleswas 373.4 inch-pounds. Additionally, the drive torque is significantlyhigher than the present fasteners as shown in FIG. 24 . The drive torquefor the comparative fastener samples is greater than 200 inch-pounds,and for most samples is greater than 250 inch-pounds. The ratio offailure torque to drive torque for the comparative fasteners is lessthan 4. Additionally, as shown by the graph of FIG. 25 and TABLE 1, thevariation in performance among the comparative samples was much higherthan the present fastener as shown by the standard deviation of thedata.

TABLE 1 Mean Standard Thread- Deviation Mean Standard Forming Thread-Failure Deviation Torque Forming Torque Failure (in-lbs) Torque (in-lbs)Torque Present disclosure, 316.6 9.8 708.1 53.4 FIG. 24 Comparativesample, 373.4 37.5 685.1 136.1 FIG. 25

The consistent performance of the present fastener provides betterpredictability. In certain applications, additional prior fasteners wereadded to accommodate the inconsistent performance of the priorfasteners. In these applications, the improved performance and decreasedvariation of the present fasteners 388 may allow a fewer number offasteners to be used to provide the desired design requirement at anincreased efficiency.

The thread-forming portion 350 of thread-forming fastener 388 may have abilobular, trilobular, quadlobular, pentalobular, hexalobular or othercross-sectional shape. Of these the pentalobular shape has been found todate to give the best performance in thread forming. In any event, theselobar shapes of the thread-forming portion of the fastener control thethread-forming torque and drive torque to facilitate installation of thefastener, reduce failures in installation, and improve the load carryingcapacity of the assembled building members. The thread-forming portionincludes a plurality of relief recesses 356 spaced around thethread-forming portion 350 to segment the thread-forming portion 350into a desired number of lobes 358 forming the bilobular, trilobular,quadlobular, pentalobular, hexalobular or other cross-sectional shape.For example, five relief recesses 356 may be spaced as desired aroundthe thread-forming portion 350 to segment the thread-forming portion 350into five lobes 358 forming the pentalobular cross-section shown in FIG.17F, and four relief recesses 145 may be spaced as desired around thethread-forming portion 143 to segment the thread-forming portion 143into four lobes 139 forming the quadlobular cross-section shown in FIG.17G. As shown in FIG. 17D, the relief recesses 356 may be longitudinalrecesses provided along the axial direction of the fastener. In onealternative, the width of the relief recesses 356 may be wider towardthe fluted lead portion forming the triangular shape as shown in FIG.17E.

In some embodiments, the thread-forming portion of the fastener includesa series of lobes 358 with relief recesses 356 between about therotational axis such as shown in FIG. 17F or 17G. Each lobe 358 has aleading portion and a tailing portion, the leading portion and firstadjacent recess may be at a first angle, shown as θ in FIG. 17F in arange from 50° to 100° from a plane tangent to the lobe adjacent theleading portion, and the tailing portion and second adjacent recess maybe at a second angle, shown as γ in FIG. 17F, in a range from 25° to 50°from a plane tangent to the lobe adjacent the tailing portion. As shownin FIG. 17F, the first angle may be greater than the second angle.Alternatively, the second angle between the tailing portion and secondadjacent recess may be in a range from 50° to 100° from a plane tangentto the lobe adjacent the tailing portion. In this alternative, the firstangle and the second angle may be approximately the same. The recess mayinclude arcuate surfaces and/or flat surfaces forming the intersectionbetween the recess and the lobe forming the first and second angles.

The relief recesses 356 may extend into the threads of the fastener toabout the minor diameter 340. Alternatively, the relief recesses 356 mayextend into the shank of the fastener deeper than the minor diameter340, such as to a depth between about 80% and 99% of the minor diameter.In yet another alternatively, the relief recesses 356 may extend intothe threads of the fastener to a depth between the major diameter 342and the minor diameter 340, such as to a depth between about 101% and120% of the minor diameter. Each relief recess 356 may be about onethread pitch in width. Alternatively, the relief recesses 356 may bebetween about 0.8 and 4 thread pitches wide. In one alternative, thewidth of the relief recesses 356 may be between about 30% and 70% of theformula (n×major diameter/number of lobes) as desired to provide desiredseparation between the lobes 358. In yet another alternative, the widthof the relief recesses 356 may be between about 40% and 60% of theformula (n×major diameter/number of lobes). For example, in oneapplication having 4 lobes (quadralobular), the width of the reliefrecesses may be approximately 60% of the formula (n×majordiameter/number of lobes). In another example, in one application having2 lobes (bilobular), the width of the relief recesses may beapproximately 50% of the formula (n×major diameter/number of lobes). Therelief recesses 356 of the thread-forming portion 350 may be betweenabout 3 to 7 thread pitches 344 in axial length. Alternatively, therelief recesses 356 of the thread-forming portion 350 may be between 2and 5 thread pitches 344 in axial length. Depending upon the size of thefastener, the thread-forming portion 350 may be between about 0.06 and0.5 inches in length, and may have a thread-forming torque of no morethan about ⅓ of the failure torque 420. In any event, the thread-formingtorque is less than the torsional strength of the fastener to avoidfailure. In one alternative, the thread-forming torque is less than 80%of the torsional strength of the fastener.

The threaded portion 348 of the thread-forming fastener 388 is adaptedto install at a drive torque 424 at least 50% less than thethread-forming torque 426, i.e. no more than 50% of the thread-formingtorque. In one alternative, the drive torque is less than 30% of thethread-forming torque. Alternatively, the drive torque 424 is betweenabout 5% and 60% of the thread-forming torque 426. To reduce drivingtorque, the threaded portion 348 may include back-tapered threads, andmay have a thread angle less than 60°, represented as a in FIG. 15C.Alternatively, the thread angle may be less than 50°. In yet anotheralternative, such thread angle may be between 45 and 50°. Reducing thethread angle also reduces the thread pitch 344 and reduces the minordiameter 340. Back-tapered threads as used herein means that the majordiameter 342 of the threaded portion 348 has a back-taper such that themajor diameter 342 is larger adjacent the thread-forming portion 350than the major diameter 342 adjacent the head 354. In certainembodiments, the back-taper of the major diameter may be between about0.0005 and 0.005 inch per inch of axial length. Alternatively, theback-taper may be between about 0.001 and 0.003 inch per inch of length.

The threaded portion 348 of fastener 388 may provide a failure torque420 of at least 343.94 inch-pounds measured using a fastener 388 havinga major diameter of ½ inch threaded into a pilot hole having at leastone diameter within nominal diameter between about 80% and 98% of themajor diameter 342 and the threaded member having a material thicknessof about 0.25 inch (about 6.35 millimeter). For material thicknessesgreater than 0.25 inch, the threaded portion may have a seating torqueof at least 400 inch-pounds. Alternatively, the threaded portion hasseating torque of at least 600 inch-pounds, and may be at least 800inch-pounds measured using a ½ inch fastener threaded into a pilot holehaving at least one diameter within nominal diameter between about 80%and 98% of the major diameter 342 and the threaded member having amaterial thickness of about 0.25 inch (about 6.35 millimeter).

The thread-forming fastener 388 may be used in connections such as shownin FIGS. 33A, 33B, 34A, and 34B, where the first steel building member,such as the joist 394, includes a clearance hole 380 having a borediameter larger than the major diameter 342 of the fastener. The secondsteel building member, such as the girder 386, includes the pilot hole378. The pilot hole 378 may have a bore diameter between about 70% and95% of the major diameter 342. Alternatively, the pilot hole 378 mayhave a bore diameter between about 80% and 98% of the major diameter,and alternatively, between about 80% and 95% of the major diameter 342.The thread-forming fastener 388 may be positioned through the clearancehole 380 in the first member and driven into the pilot hole 378 of thesecond member. The thread-forming portion 350 forms threads in the boreof the pilot hole enabling the threaded portion 348 to be threaded intothe second member, clamping the first member between the head 354 andthe threads formed in the second member. The thread-forming fastener 388may have a major diameter between about ¼ inch and 1 inch, or greater asdesired for the size and load requirements for the connection in theassembly. At least a portion of the threaded portion 348 of thethread-forming fastener 388 as shown in FIGS. 16 and 17 may comply withASTM A307, A354, A325, A490, or other fastener standard as required.

Alternatively, for certain connections, both the first member and thesecond member may include the pilot hole 378, wherein the thread-formingportion 350 forms threads in both the first and second members.

The self-drilling, thread-forming fastener 362, as shown in FIGS. 18Athrough 19D, are fasteners of steel comprising the head 354 capable ofclamping the first steel building member to the second steel buildingmember with the fastener installed. The self-drilling, thread-formingfastener 362 includes the threaded portion 348 adjacent the head 354,and the thread-forming portion 350 as discussed above adjacent thethreaded portion 348 of at least HRC 50 hardness adapted to enable thefastener form threads into at least the second building member. Theself-drilling, thread-forming fastener 362 has a fluted lead portion 360at the tip of the fastener 362 and adjacent the thread-forming portion350 of at least HRC 50 hardness with a nominal diameter between about 70and 95% of the major diameter 342 of the threaded portion 348 adapted toform the fastener opening, or pilot hole 378, and typically larger thanthe minor diameter, although for thin metal applications, such asthinner than 14 gage, or less than 16 gage, the nominal diameter of thefluted lead portion 360 may be smaller than the minor diameter.Alternatively, the fluted lead portion 360 has a nominal diameterbetween about 80% and 95% of the major diameter 342.

The fluted lead portion 360 may have a swaged or pinched point, a milledpoint, or a combination of both. The milled point alone, or incombination with preformed swedged or pinched point, is generallydesired to ensure effectiveness of the fluted lead portion in drillingthrough the building members. The length of the fluted lead portion 360may be longer than the thickness of the building member through whichthe fluted lead portion drills. It may be useful to provide the flutedlead portion 360 having an axial length between about 1.1 and 2.0 timesthe thickness of the drilled building member. The fluted lead portion360 may be a Type 1, Type 2, Type 3, Type 4, Type 5, or a variationthereof.

At least a portion of the threaded portion 348 of the self-drilling,thread-forming fastener 362 may have a hardness between about HRB 70 andHRC 40 through hardness. In one alternative, at least a portion of thethreaded portion 348 has a hardness between about HRC 25 and HRC 34. Inone alternative, at least a portion of the threaded portion 348 has athrough hardness between about HRB 70 and HRB 100. In one alternative,at least a portion of the threaded portion 348 has a through hardnessbetween about HRC 19 and HRC 30. In one alternative, at least a portionof the threaded portion 348 has a through hardness between about HRC 26and HRC 36. In yet another alternative, at least a portion of thethreaded portion 348 has a through hardness between about HRC 33 and HRC39. As discussed above, the hardness of the threaded portion 348 may beselected to comply with ASTM A307, ASTM A325, ASTM A354, ASTM A490 orother fastener standard. Alternatively or in addition, the hardness ofthe threaded portion 348 may be selected to comply with SAE J429 Grade2, SAE J429 Grade 5, and SAE J429 Grade 8, or other fastener standard.

In yet another alternative, the self-drilling, thread-forming fastenermay be case hardened to at least HRC 50. For certain applications, theself-drilling, thread-forming fastener may be a case hardened fastener.In the figures, such as FIGS. 15 and 16 , in which under certainapplications may utilize a case hardened self-drilling, thread-formingfastener, the fastener will be referenced as a case hardenedself-drilling, thread-forming fastener 396. The case hardenedself-drilling, thread-forming fastener 396 may have a major diameter 342of between about 0.18 and 0.26 inch.

Adjacent the thread-forming portion 350, a portion of the threadedportion 348 may have a hardness greater than about HRC 50, and may begreater than about HRC 54. Up to five threads between the threadedportion and the thread-forming portion 350 may be hardened to at leastHRC 50 or at least HRC 54. The threaded portion 348 of theself-drilling, thread-forming fastener 362 may be through-hardened suchthat the fastener is ductile through the threaded portion. As discussedabove, as the self-drilling, thread-forming fastener 362 is installedconnecting a first steel building member and a second steel buildingmember, the fastener 388 may be tightened to clamp the first memberbetween the head 354 and the formed threads in the second buildingmember. As the thread-forming fastener 388 is tightened, a portion ofthe threaded portion 348 between the head 354 and the threads engagingthe second building member elongate providing a clamping load on theconnection according to design requirements. The present thread-formingfasteners 388 have sufficient ductility for structural connections suchas slip-critical connections.

The self-drilling, thread-forming fastener 362 typically has a majordiameter between about 0.12 inch and about ½ inch. In certain instances,the size of the fastener 362 may be limited by the ability of the flutedlead portion 360 to function in drilling at larger sizes. In aconnection between a first and a second building member, the firstbuilding member may have a clearance hole 380 having a diameter largerthan the major diameter of the fastener 362. The self-drilling,thread-forming fastener 362 is installed through the clearance hole androtated into the second member. The fluted lead portion 360 drills anopening through the second member, and the thread-forming portion 350forms threads in the bore of the drilled fastener opening for thethreaded portion 348 to engage the second building member. Theself-drilling, thread-forming fastener 362 is tightened to clamp thefirst member between the head 354 and the threads formed in the secondmember. The threaded second member acts as a nut, and in certainapplications, no nut may be required based on design requirements.Alternatively, the self-drilling, thread-forming fastener 362 may beinstalled in a pilot hole, and the thread-forming portion 350 formsthreads in the bore of the pilot hole for the threaded portion 348 toengage the second building member. In yet another alternative, neitherclearance hole or pilot hole is provided and the fluted lead portion 360drills through both the first and second member, and the thread-formingportion 350 forms threads in the bore of the drilled fastener openingfor the threaded portion 348 to engage with the formed threads in boththe first and second members. Optionally, the self-drilling,thread-forming fastener 362 may include an unthreaded shank portionbetween the head 354 and the threaded portion 348 as desired for theconnection. If provided, the length of an unthreaded shank portion andthe axial length of the threaded portion 348 may be selected accordingto the thickness of the first and second building members and desiredlength of thread engagement. For example, in certain bearing-typeconnections with threads excluded from the shear plane, an unthreadedshank portion may be desired having a length greater than the thicknessof the first building member such that the threaded portion 348 engagesthe second building member clamping the first building member betweenthe head 354 and the threads engaging the second building member. In anycase, the threaded engagement with the first and/or second buildingmember acts as a nut, and for certain applications, no nut may berequired based on design requirements. Examples of variousconfigurations of installation of self-drilling, thread-forming fastener362 with and without clearance holes and/or pilot holes are disclosed inapplications described herein, and each application disclosed is notlimited to the configuration described.

The present self-drilling, thread-forming fastener 362, 396 provides aratio of strip torque to thread-forming torque of at least 3.0 and aratio of strip torque to drive torque greater than 6.0 over a range ofcombined thickness of first and second steel building members from 0.036inch to 0.084 inch. As shown in FIG. 26A, samples of a ¼ inch majordiameter self-drilling, thread-forming fastener 362 of the presentdisclosure identified as manufacturer's samples ETC045 were installedinto materials of different thicknesses and compared to prior ¼ inchmajor diameter fasteners. For steel sheet samples between 26 gage and 16gage, the fasteners were installed into two sheets together.Additionally, the fasteners were installed into one steel sheetthickness for materials between about 0.109 and 0.25 inch thickness. Tensamples were used for each tested thickness. TABLE 2 shows typical gagethickness for steel sheet (source: Steel Deck Institute).

TABLE 2 TWO ONE SHEET SHEET GAGE THICKNESS THICKNESS 16 .0598 0.120 18.0474 0.096 20 .0358 0.072 22 .0295 0.060 24 .0238 0.048 26 .0179 0.036

FIG. 26A and TABLE 3 show the ratio of strip torque to thread-formingtorque for the tested fasteners. The ¼ inch self-drilling,thread-forming fastener 362 provided a ratio of strip torque tothread-forming torque of at least 3.0 for all thicknesses tested up toand including 0.143 inch thick sheet. Alternatively, the ¼ inchself-drilling, thread-forming fastener 362 provided a ratio of striptorque to thread-forming torque of at least 3.5 for all thicknessestested up to and including 0.143 inch thick sheet. TABLE 4 provides thestrip torque and thread-forming torque for the ¼ inch samples tested.

TABLE 3 ¼ inch ¼ inch Present Comparative Disclosure Sample Strip Torqueto Strip Torque to Thread-forming Thread-forming Torque Ratio TorqueRatio 26/26 gage 4.01 4.00 24/24 gage 3.73 3.42 22/22 gage 3.56 2.9620/20 gage 4.19 1.95 18/18 gage 4.23 2.27 16/16 gage 4.67 2.43 0.1094.18 2.78 0.113 4.67 2.95 0.123 5.00 2.59 0.133 5.27 2.84 0.143 4.292.84 0.155 2.96 2.94 0.170 2.46 2.26 0.187 2.19 2.23 0.205 2.39 2.180.250 1.62 2.09

TABLE 4 ¼ inch ¼ inch ¼ inch ¼ inch Present Present ComparativeComparative Disclosure Disclosure Sample Sample Thread-forming StripThread-forming Strip Torque Torque (in-lb) Torque (in-lb) Torque (in-lb)(in-lb) 26/26 9.73 38.98 3.18 12.73 gage 24/24 14.84 55.37 7.43 25.43gage 22/22 18.01 64.17 10.97 32.43 gage 20/20 13.13 55.06 11.38 22.16gage 18/18 19.69 83.24 18.27 41.55 gage 16/16 26.61 124.25 24.37 59.22gage 0.109 51.14 213.89 36.8 102.37 0.113 55.80 260.42 35.16 103.7 0.12356.01 280.28 41.73 107.98 0.133 57.53 303.09 43.34 123.17 0.143 66.68285.87 45.79 130.26 0.155 94.43 279.12 46.99 138.33 0.170 116.35 286.4870.25 158.82 0.187 114.43 250.67 74.78 167.03 0.205 115.50 275.52 84.04182.91 0.250 131.23 212.22 108.13 225.76

The ratio of strip torque to thread-forming torque is at least 3.0 and aratio of strip torque to drive torque greater than 6.0 over a range ofcombined thickness of first and second steel building members from 0.036inch to 0.084 inch. Alternatively, the present self-drilling,thread-forming fasteners 362, 396 may have a ratio of strip torque tothread-forming torque of at least 3.0 and a ratio of strip torque todrive torque greater than 8.0 over a range of combined thickness offirst and second steel building members from 0.036 inch to 0.084 inch.Alternatively, the fasteners may have a ratio of strip torque tothread-forming torque of at least 3.5 and a ratio of strip torque todrive torque greater than 6.0 over a range of combined thickness offirst and second steel building members from 0.036 inch to 0.084 inch.In yet another alternative, the ratio of strip torque to thread-formingtorque may be at least 3.5 and a ratio of strip torque to drive torquegreater than 8.0 over a range of combined thickness of first and secondsteel building members from 0.036 inch to 0.084 inch. In yet anotheralternative, the ratio of strip torque to thread-forming torque may beat least 3.0 and a ratio of strip torque to drive torque greater than4.0 over a range of combined thickness of first and second steelbuilding members from 0.036 inch to 0.108 inch. In another alternative,the fasteners may have a ratio of strip torque to thread-forming torqueof at least 3.0 and a ratio of strip torque to drive torque greater than6.0 over a range of combined thickness of first and second steelbuilding members from 0.036 inch to 0.108 inch. Alternatively, thepresent self-drilling, thread-forming fasteners 362, 396 may have aratio of strip torque to thread-forming torque of at least 4.0 and aratio of strip torque to drive torque greater than 8.0 over a range ofcombined thickness of first and second steel building members from 0.054inch to 0.084 inch. Alternatively, the fasteners may provide a ratio ofstrip torque to thread-forming torque of at least 4.0 and a ratio ofstrip torque to drive torque greater than 10.0 over a range of combinedthickness of first and second steel building members from 0.054 inch to0.084 inch.

For certain applications, the self-drilling, thread-forming fasteners362, 396 are capable of providing a ratio of failure torque tothread-forming torque of at least 3.0 and a ratio of failure torque todrive torque greater than 6.0 over a range of combined thickness offirst and second steel building members from 0.10 inch to 0.32 inch. Asshown in FIG. 26B, samples of a ⅜ inch major diameter self-drilling,thread-forming fastener 362 of the present disclosure identified asmanufacturer's samples 360-80952-60 were installed into a 0.302 diameterpilot hole in materials of different thicknesses and compared to prior ⅜inch major diameter fasteners. The fastener samples were installed intosingle steel sheet thicknesses between about 0.109 and 0.25 inchthickness. Ten samples were used for each tested thickness. TABLE 5shows the ratio of strip torque to thread-forming torque for the testedfasteners. The ⅜ inch self-drilling, thread-forming fastener 362provided a ratio of strip torque to thread-forming torque of at least3.0 for all thicknesses tested up to and including 0.187 inch thicksheet. TABLE 6 shows the failure torque and the thread-forming torquefor the ⅜ inch samples tested.

TABLE 5 ⅜ inch ⅜ inch Present Comparative Disclosure Sample Strip Torqueto Strip Torque to Thread-forming Thread-forming Torque Ratio TorqueRatio 0.109 4.54 3.15 0.113 4.34 2.83 0.123 4.32 3.00 0.133 4.17 3.230.143 4.07 3.04 0.155 3.95 2.92 0.170 3.75 2.53 0.187 3.00 2.35 0.2052.68 2.08 0.250 2.24 1.83

TABLE 6 ⅜ inch ⅜ inch ⅜ inch ⅜ inch Present Disclosure ComparativeComparative Disclosure Invention Sample Sample Thread-forming StripTorque Thread-forming Strip Torque Torque (in-lb) (in-lb) Torque (in-lb)(in-lb) 0.109 121.83 552.62 165.35 520.63 0.113 128.16 556.18 188.02531.63 0.123 136.25 576.89 182.13 545.9 0.133 149.72 625 188.02 608.060.143 176.16 716.7 192 583.56 0.155 186.66 737.11 236.14 690.14 0.170214.49 804.78 286.1 724.11 0.187 223.23 668.83 266.83 673.98 0.205266.46 713.15 342.96 712.69 0.250 316.59 708.05 373.44 685.13

As shown in FIG. 26B and TABLE 4, the ratio of failure torque tothread-forming torque of at least 3.0 for samples tested in materialthicknesses from 0.109 through 0.187. It is contemplated that fastenerswith the present thread-forming portion can obtain a ratio of failuretorque to thread-forming torque of at least 3.0 up to thicknesses of0.32.

As shown in the graph of FIG. 27 , the self-drilling, thread-formingfastener 362 has a drilling torque to rotate the fluted lead portion 360into the first and second building members forming the fastener opening.Additionally, the drive torque 424 is at least 50% less than thethread-forming torque 426. As discussed above, the drive torque 424 maybe between about 5% and 60% of the thread-forming torque 426. Theself-drilling, thread-forming fasteners 362 have the added advantage ofincreased back-out resistance and are less likely to come loose byvibration.

The installation torque over time for the self-drilling, thread-formingfastener 362 was measured and shown in FIG. 27 . Five samples identifiedas manufacturer's samples ETC040 having a major diameter of ¼ inch wereinstalled at 175 revolutions per minute into pilot holes correspondingto the fluted lead portion 360 into first and second steel membershaving a combined thickness of about 0.06 inch. The thread-formingtorque 426 as shown in the graph of FIG. 27 is less than about 20inch-pounds. Alternatively, the thread-forming torque 426 may be lessthan about 15 inch-pounds. The drive torque 424, before the torque risesto seating, is less than about 6 inch-pounds. The failure torque 420 isgreater than 40 inch-pounds. For certain samples, the failure torque isgreater than 50 inch-pounds, and one sample greater than about 60inch-pounds. The failure torque 420 shown in FIG. 27 is a strip torque.The ratio of strip torque to thread-forming torque may be at least 3.0and the ratio of strip torque to drive torque is greater than 6.0 whenthe first and second steel members have a combined thickness of 0.06inch (about 1.5 millimeter) and the nominal diameter of the fluted leadportion 360 is between 70 and 95% of major diameter. Alternatively, theratio of strip torque to thread-forming torque may be at least 3.0 andthe ratio of strip torque to drive torque is greater than 6.0 when thefirst and second steel members have a combined thickness of 0.06 inch(about 1.5 millimeter) and the nominal diameter of the fluted leadportion 360 is between 70 and 95% of major diameter. The ratio of striptorque to drive torque may be greater than 10.

Further testing of ¼ inch major diameter self-drilling, thread-formingfasteners 362 is shown in FIG. 28 . As with the experiment shown in FIG.27 , the installation torque over time for the self-drilling,thread-forming fastener 362 was measured using ten samples identified asmanufacturer's samples ETC045 having a major diameter of ¼ inchinstalled at 175 revolutions per minute into two 22 gage steel membershaving a combined thickness of about 0.06 inch and plotted in the graphof FIG. 28 . In this test sample, the average thread-forming torque 426of the samples was 18 inch-pounds. As shown in the graph of FIG. 28 ,the thread-forming torque is less than about 20 inch-pounds. The drivetorque 424, before the torque rises to seating, is less than about 10inch-pounds. The failure torque 420 is greater than 60 inch-pounds. Forcertain samples, the failure torque is greater than 65 inch-pounds, andone sample greater than 70 inch-pounds. The average failure torque forthe tested samples of the present ¼ fastener was 64.2 inch-pounds.

FIG. 29 shows installation torque over time for comparative samples ofprior ¼ inch fasteners. The comparative fasteners lacked the presentthread-forming portion, instead utilizing prior technology. The graph ofFIG. 29 shows the significantly lower failure torque of the ten samples.The average failure torque for the tested comparative ¼ inch samples was32.4 inch-pounds.

The present self-drilling, thread-forming fastener 362, 396 provides alarger seating torque window than prior fasteners in certainapplications. The seating torque window is one measure for a range ofseating torques in which the fastener may be installed providing adesired clamping and inhibiting stripping of the fastener or otherfastener failure. FIGS. 30A through 30D show seating torque windows forpresent and comparative test samples installed in two thicknesses of 24gage material (FIG. 30A), two thicknesses of 22 gage material (FIG.30B), two thicknesses of 20 gage material (FIG. 30C), and twothicknesses of 22 gage material (FIG. 30D) as examples of improvementsin seating torque. The seating torque window is calculated using thetest data for strip torque minus three standard deviations of the striptorque data for the upper limit, and the thread-forming torque minusthree standard deviations of the thread-forming torque for the lowerlimit. In the test shown in FIG. 30C, the competitive samples varied sogreatly in failure torque that three standard deviations from the striptorque was lower than the thread-forming torque, shown by a negativetorque window in the table in FIG. 30C. The improved consistency andperformance of the present fasteners provides a greater seating torquewindow for certain applications. The larger seating torque windowprovides a larger seating target for various operators and variousfastener drivers to achieve.

Test results for samples of ⅜ inch major diameter self-drilling,thread-forming fasteners 362 is shown in FIG. 31 . The installationtorque over time for the self-drilling, thread-forming fastener 362 wasmeasured using ten samples identified as manufacturer's samples360-80952-60 having a major diameter of ⅜ inch installed at 175revolutions per minute into a single sheet of 0.187 inch thick materialand plotted in the graph of FIG. 31 . In this test sample, the averagethread-forming torque 426 of the samples was 223.2 inch-pounds. As shownin the graph of FIG. 31 , the thread-forming torque is less than about250 inch-pounds. The drive torque 424, before the torque rises toseating, is less than about 50 inch-pounds. The failure torque 420 isgreater than 600 inch-pounds. For certain samples, the failure torque isgreater than 650 inch-pounds, and several samples were greater than 700inch-pounds. The average failure torque for the tested samples of thepresent ⅜ fastener was 668.8 inch-pounds.

FIG. 32 shows installation torque over time for comparative samples ofthe prior ⅜ inch fasteners in 0.187 thick material. The graph of FIG. 32shows higher thread-forming torque required to drive the priorfasteners. The average thread-forming torque of the ten samples was286.8 inch-pounds. Additionally, the drive torque is significantlyhigher than the present fasteners as shown in FIG. 31 . The drive torquefor the comparative fastener samples is greater than 125 inch-pounds,and for most samples is greater than 150 inch-pounds. The ratio offailure torque to drive torque for the comparative fasteners is lessthan about 5.

To increase the strip torque when the threaded building member is a thinmaterial such as less than 14 gage, or less than 16 gage, the threadedportion 348 may extend to the head 354 such that the major diameter 342of the threaded portion 348 is extending to within 1.5 of the threadpitch of the head 354, as indicated in the detail of FIG. 18A byreference 352. Alternatively, the major diameter extends to within 1.2thread pitches of the head 354. In yet another alternative, the majordiameter 342 extends to within about one thread pitch of the head.Optionally, the head 354 of the fastener may be undercut such as shownin the detail of FIG. 19A approximately adjacent where the threadedportion joins the head and adapted to deform the first steel buildingmember on tightening of the fastener. Alternatively, the fastener may beundercut and adapted to deform the first and second steel buildingmember on tightening of the fastener. The undercut may include a radius343 at least about 0.02 inch radius, and may be at least about 0.03 inchradius adjacent where the threaded portion joins the head.Alternatively, or in addition, a serrated surface may be provided on theunderside of the head 354 to engage the surface of the first steelbuilding member. The serrated surface may comprise serrations,projections, nibs, or other deformations or protrusions as desiredpositioned on the underside of the head 354, and may be positioned inthe undercut, if provided.

In one alternative, the head is undercut adjacent where the threadedportion joins the head and the major diameter of the threaded portionextends to within 1.5 of the thread pitch of the head. The closeproximity of the threads to the underside of the head further assiststhe deformation of at least the first steel building member into theundercut on tightening of the fastener. We have found that thedeformation of at least the first building member into the undercutimproves the connection strength by increasing the strip torque andinhibiting failure modes caused by tipping of the fastener under sheetsheer when the threaded building member is a thin material such as lessthan 14 gage, or less than 16 gage. In certain applications, theimproved performance the present fasteners 362, 396 may allow a fewernumber of fasteners to be used to provide the desired design requirementat an increased efficiency.

The threaded portion 348 of fastener 362 may provide a seating torque ofat least 420 inch-pounds measured using a fastener 362 having a majordiameter of about ¼ inch with the fluted lead portion 360 having atleast one diameter within nominal diameter between about 80% and 95% ofthe major diameter 342 and installed in a first and second buildingmember having a combined material thickness of at least 0.125 inch(about 3.2 millimeter). Alternatively, the threaded portion has seatingtorque of at least 100 inch-pounds, and may be at least 120 inch-poundsmeasured using a ¼ inch fastener with the fluted lead portion 360 havingat least one diameter within nominal diameter between about 80% and 95%of the major diameter 342 and installed in a first and second buildingmember having a combined material thickness of at least 0.125 inch(about 3.2 millimeter).

For larger diameter self-drilling, thread-forming fasteners 362 such ashaving a major diameter 342 of ⅜ inch, the threaded portion 348 offastener 388 may provide a failure torque 420 of at least 600inch-pounds measured using a fastener 362 having a major diameter of ⅜inch and a fluted lead portion 360 having a nominal diameter betweenabout 80% and 98% of the major diameter 342 and the threaded memberhaving a material thickness of about 0.25 inch (about 6.35 millimeter).For material thicknesses greater than 0.25 inch, the threaded portionmay have a seating torque of at least 400 inch-pounds. Alternatively,the threaded portion has seating torque of at least 600 inch-pounds, andmay be at least 800 inch-pounds measured using a ⅜ inch fastener havinga fluted lead portion 360 having a nominal diameter between about 80%and 98% of the major diameter 342 and the threaded member having amaterial thickness of about 0.25 inch (about 6.35 millimeter).

As discussed above, the threaded portion 348 of the thread-formingfasteners 388 and self-drilling, thread-forming fastener 362, 396 mayinclude back-tapered threads, and may have a thread angle less than 60°.Alternatively, the thread angle may be less than 50°. In yet anotheralternative, the threads may have a thread angle between 45 and 50°. Theback-taper of the major diameter may be between about 0.0005 and 0.005inch per inch of axial length. Alternatively, the back-taper of majordiameter may be between about 0.001 and 0.003 inch per inch of length.In the past, the thread portion of fasteners used for buildingstructures typically had a pitch angle of 60°. We have found that thedrive torque required to drive prior self-tapping fasteners afterthread-forming was nearly the same as the thread-forming torque. This isa disadvantage because for larger fasteners, such as about ½ inch majordiameter fasteners and greater, an impact driver typically is requiredto drive the fasteners. While an impact driver delivers sufficienttorque to drive the prior fasteners, the time required to impact a largebolt into a structural member in the past was not commerciallypractical. The present fasteners 388, 362 may require an impact driverto provide the thread-forming torque 426 to advance the thread-formingportion 350 into the fastener opening, but the drive torque 424 of thepresent fasteners is sufficiently lower than the thread-forming torque426 that the driver may easily turn the threaded portion 348 into thefastener opening without binding and engaging the impact mechanism. Withthe impact mechanism disengaged while installing the threaded portion,the fastener may be rapidly installed. Alternatively, the threading 426torque may be low enough that an impact driver is not required and adrill driver may be used.

The thread-forming fastener 388 and the self-drilling, thread-formingfastener 362 may be nutable, i.e., adapted to thread a nut on thefastener. For a nut to be threaded onto the fastener 388, 362, the majordiameter 342 of the thread-forming portion 350 may be about the samediameter or smaller than the major diameter of the threaded portion 348.The thread profile of the thread-forming portion 350 corresponds to thethreaded portion 348 to enable the nut to be threaded over thethread-forming portion. Additionally, for a nutable self-drilling,thread-forming fastener 362, the fluted lead portion 360 has a nominaldiameter smaller than the minor diameter of the corresponding nut suchthat the nut will pass over the fluted lead portion 360.

In one alternative, the thread-forming fasteners 388 and theself-drilling, thread-forming fasteners 362 may be configured to be usedin place of bolt-and-nut fasteners without changing the hole sizes andhole placement in the building members. The major diameter of thethreaded portion 348 may be selected to be installed into standard-sizepunched or drilled holes provided in the building members. For example,a building connection designed for a ½ inch bolt-and-nut fastener may befabricated with punched holes having a diameter of 9/16 inch. Thethread-forming fasteners 388 and the self-drilling, thread-formingfasteners 362 may be configured to have a major diameter of ⅝ inch, or11/16 inch, or other major diameter providing thread engagement andseating torque as desired. By configuring the thread-forming fasteners388 and the self-drilling, thread-forming fasteners 362, fabricators cancontinue producing the building members using standard-size punches ordrills without costly re-tooling. It is contemplated that fasteners ofthis configuration may increase the capacity of the connection by 15% to30% over prior art standard nut-and-bolt fasteners through the same sizepilot hole, and in turn, can reduce the number of fasteners to carry thesame load by 15% to 30%.

For certain bolted connections, the threaded portion 348 of the fastenermust comply with fastener standards such as ASTM A307, ASTM A325, ASTMA354, ASTM A490, SAE J429 Grade 2, SAE J429 Grade 5, SAE J429 Grade 8,or other fastener standards. In the past, case hardened self-drillingfasteners and self-threading fasteners could not comply with thesestandards because of the case hardness of the prior fasteners. Priorfasteners were case hardened over the whole fastener reducing ductilityand preventing their use in many structural applications. The presentfasteners 388, 362 overcome some of the problems of the prior fastenersby selectively hardening portions of the fastener. Portions of thepresent fasteners 388, 362 may be selectively hardened, such as thetapered lead portion 346, fluted lead portion 360, and thethread-forming portion 350 to a hardness of at least HRC 50.Additionally, between about 1 and 5 threads between the threaded portion348 and the thread-forming portion 350 may be hardened to at least HRC50. By hardening only a portion of the fastener to at least HRC 50, theportion of the threaded portion 348 making the bolted connection may beprovided with physical properties as desired in compliance with ASTMA307, ASTM A325, ASTM A354, ASTM A490, SAE J429 Grade 2, SAE J429 Grade5, SAE J429 Grade 8 or other selected fastener standards. Typically, thefasteners 388, 362 are made with a medium carbon steel, medium carbonalloy steel, or a weathering steel in conformance with the desiredfastener standard.

In one alternative, the floor joist system 400 may be a composite walland floor joist system such as disclosed in U.S. patent application Ser.No. 12/019,372, filed Jan. 24, 2008 and published as U.S. 2009/0188187A1. The floor joist system 400 may include the steel deck 382, fastenedto the joists 394 using self-drilling, thread-forming fasteners 396.Additionally, self-drilling, thread-forming stand-off screws 3398 may beprovided through the deck 382 and joist 394 adapted to be encapsulatedwithin the concrete slab 384 providing a composite joist floor asdisclosed in U.S. patent application Ser. No. 12/019,372.

The self-drilling, thread-forming stand-off screws 398 as shown in FIGS.20A-22 typically have a major diameter between about 0.12 inch and about⅜ inch. The self-drilling, thread-forming stand-off screws 398 mayinclude the head 354, a stand-off portion 364 having a desired length, aseat portion 359, the threaded portion 348 as discussed above adjacentthe seat portion, and the thread-forming portion 350 as discussed aboveadjacent the threaded portion 348 adapted to enable the fastener toengage with formed threads in a building member. The seat portion 359may be a SEMS washer positioned adjacent the stand-off portion 364. ASEMS washer includes a washer or other member held captive on thefastener where the dimension of the fastener on each side of the SEMSwasher being larger than the washer hole prevents the SEMS washer fromcoming off. Alternatively, the seat portion may be a flange integral tothe stand-off portion 364. In yet another alternative, the seat portion359 of the self-drilling, thread-forming stand-off screws 398 mayinclude the head. As shown in FIG. 22 , the self-drilling,thread-forming stand-off screws 398 may include an anchor member 355formed integrally with the stand-off portion 398. The anchor member 355may be a rolled collar as shown in FIG. 22 .

As illustrated in FIG. 20B, the seat portion 359 may include serrations351 adjacent the threaded portion 348 to engage the surface of the steeldeck 382 or other building member during installation. Theself-drilling, thread-forming stand-off screws 398 has the fluted leadportion 360 as discussed above adjacent the thread-forming portion 350with a nominal diameter between about 70 and 95% of the major diameter342 of the threaded portion adapted to form the fastener opening 378.The self-drilling, thread-forming stand-off screws 398 is installedthrough the steel deck 382 into the joist 394 or other building member.The fluted lead portion 360 drills through the steel deck 382 and joist,and the thread-forming portion 350 forms threads in the bore of thedrilled fastener opening for the threaded portion 348 to engage thejoist 394. The self-drilling, thread-forming stand-off screws 398 istightened to clamp the deck 382 between the seat portion 359 and thethreads in the joist 394 or other building member.

As shown in FIGS. 31A, 31B, 32A, and 32B, the joists 394 may beconnected to the load bearing building member 410 such as the girder 386using thread-forming fasteners 388. When connecting structural membersusing the thread-forming fasteners 388, the first member is providedwith a clearance hole 380 larger in diameter than the major diameter ofthe fastener 388, and the second member is provided with the pilot hole378 smaller in diameter than the major diameter of the fastener,typically between 80 and 98% of the major diameter 342, and typicallylarger than the minor diameter of the fastener 388. The joist 394includes a joist seat 390 through which the joist 394 may be connectedto the girder 386 or other load bearing member 410. As shown in FIGS.31A, 31B, 32A, and 32B, various configurations of joist seats may beused as desired. The joist seat 390 includes one or more clearance holes380 for fastening the joist to the load bearing member. To install thejoist 394 to the girder 386 or other load bearing member, the fastener388 positioned in the clearance hole 380 in the joist is driven into thepre-drilled hole 378 in the girder. The thread-forming portion 350 formsthreads in the hole 378 enabling the threaded hole in the girder to actas a nut to clamp the joist seat between the girder and the head 354 ofthe fastener. Optionally, a nut may be provided and threaded onto thefastener 388 and tightened as desired.

In the past, joists were fastened to the load bearing member by weldingor by a bolt-and-nut connection. The bolts used for fastening joiststypically comply with ASTM A307, A354, or A325. Bolt-and-nut connectionsrequire the installer to reach both sides of the connection to hold thenut while the bolt turns. Additionally, welded connections have been adisadvantage because a trained welder must be present and perform theweld connections. The presently disclosed thread-forming fasteners 388and self-drilling, thread-forming fastener 362 overcome these and otherdisadvantages, and may be installed from the top side of the joists 394.The present fasteners 388, 362 increase the speed of joist installationand decrease cost.

While certain embodiments have been described, it must be understoodthat various changes may be made and equivalents may be substitutedwithout departing from the spirit or scope of the present disclosure. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the disclosure without departing fromits spirit or scope.

What is claimed is:
 1. A fastener comprising: a standoff portion havinga first shank portion and a second shank portion; a first head portionhaving a key shape formed on the standoff portion between the firstshank portion and the second shank portion; the key shape capable ofaccepting torque from a drive oriented on a drive axis of the fastener;a seat between the second shank portion and a screw portion, the screwportion extending from the seat in a direction of the drive axis of thefastener; the seat separated from the first head portion by the secondshank portion; the screw portion separated from the first head portionby the second shank portion and having a fluted lead end, and athread-forming portion having lobes adapted to enable formation ofthreads into a metal structure; a threaded portion having threadsopposite the screw portion; and a second head portion between the firsthead portion and the screw portion, the second head portion having a keyshape where the key shape of the second head portion is different thanthe key shape of the first head portion.
 2. The fastener of claim 1where the seat has a diameter larger than the first shank portion andthe second shank portion.
 3. The fastener of claim 2 where a diameter ofthe seat is larger than the diameter of the first head portion.
 4. Thefastener of claim 1 where a diameter of the second head portion islarger than a diameter of the first head portion.
 5. The fastener ofclaim 1 where the second head portion is separated from the first headportion by the second shank portion.
 6. The fastener of claim 1 wherethe second head portion further comprises the seat where the key shapeof the second head portion is between the seat and the first headportion.
 7. The fastener of claim 1 where the first head portion isencapsulated by concrete as an anchor.
 8. A fastener comprising: astandoff portion having a first shank portion and a second shankportion; a first head portion having a key shape formed on the standoffportion between the first shank portion and the second shank portion;the key shape capable of accepting torque from a drive oriented on adrive axis of the fastener; a seat between the second shank portion anda screw portion, the screw portion extending from the seat in adirection of the drive axis of the fastener; the seat separated from thefirst head portion by the second shank portion; the screw portionseparated from the first head portion by the second shank portion andhaving a fluted lead end, and a thread-forming portion having lobesadapted to enable formation of threads into a metal structure; athreaded portion having threads opposite the screw portion; and a secondhead portion between the first head portion and the screw portion wherea diameter of the second head portion is larger than a diameter of thefirst head portion.
 9. The fastener of claim 8 where the seat has adiameter larger than the first shank portion and the second shankportion.
 10. The fastener of claim 9 where a diameter of the seat islarger than the diameter of the first head portion.
 11. The fastener ofclaim 8 where the second head portion is separated from the first headportion by the second shank portion.
 12. The fastener of claim 8 wherethe second head portion further comprises the seat where the key shapeof the second head portion is between the seat and the first headportion.
 13. The fastener of claim 8 where the first head portion isencapsulated by concrete as an anchor.
 14. A fastener comprising: astandoff portion having a first shank portion and a second shankportion; a first head portion having a key shape formed on the standoffportion between the first shank portion and the second shank portion;the key shape capable of accepting torque from a drive oriented on adrive axis of the fastener; a seat between the second shank portion anda screw portion, the screw portion extending from the seat in adirection of the drive axis of the fastener; the seat separated from thefirst head portion by the second shank portion; the screw portionseparated from the first head portion by the second shank portion andhaving a fluted lead end, and a thread-forming portion having lobesadapted to enable formation of threads into a metal structure; and wherethe first head portion is encapsulated by concrete as an anchor.
 15. Thefastener of claim 14 further comprising a threaded portion havingthreads opposite the screw portion.
 16. The fastener of claim 14 wherethe seat has a diameter larger than the first shank portion and thesecond shank portion.
 17. The fastener of claim 16 where a diameter ofthe seat is larger than the diameter of the first head portion.
 18. Thefastener of claim 15 comprising a second head portion having a key shapebetween the first head portion and the screw portion.
 19. The fastenerof claim 18 where the second head portion is separated from the firsthead portion by the second shank portion.
 20. The fastener of claim 18where the second head portion further comprises the seat where the keyshape of the second head portion is between the seat and the first headportion.